High-voltage (HV) relays are a means of protecting a high-voltage circuit in a power system by tripping a circuit breaker when a fault is detected. Because of the key part that it plays in a variety of industries. HV relay protection testing makes excellent business sense. In a state-of-the-art installation, testing the digital or numerical protection relay includes software as well as hardware. This process is far more complex than testing a static or electromechanical relay.
Why is Testing Required?
Regular testing is essential to keep costs down while identifying issues at an early stage. Specifically, testing is done to:
- avoid surges and spikes;
- monitor power quality issues which may lead to data loss;
- monitor problems that may result in excessive electrical costs; and
- reduce insurance costs through certification.
It is essential to ensure that relays are properly calibrated. If the relay is too sensitive, your power system can trip unnecessarily and cause downtime. On the other hand, you do not want to have the relay so rigidly so that a problem is missed. “The impact of such errors may range from simply being a nuisance (tripping occurs repeatedly on energisation, requiring investigation to locate and correct the errors) through to failure to trip under fault conditions, leading to major equipment damage, disruption to supplies and potential hazards to personnel,” according to the Electrical Engineering Portal (EEP).
Interface relays can be classified into three categories: insulation voltage, type of galvanic isolation module, and the operational speed. These three properties define most interface relays:
- low level (0 kV to 10 kV)
- medium level (10 to 100 kV)
- high level (above 100 kV)
- electromagnetic (transformer)
- radio frequency
- mechanical transmission
Speed of Execution
- super fast (up to 100 microseconds)
- fast (100 microseconds to 3 milliseconds)
- inertial (above 3 milliseconds)
How to Schedule HV Relay Protection Testing
Companies can schedule the HV relay protection testing in several ways: after the relays have been installed but before they are first used, at regular intervals during their use (every 2 years), and according to the schedule set by government standards. While it may seem unnecessary to test the HV relay immediately after installation, companies must consider the ramifications if the device was wired incorrectly or has suffered damage during shipping. Safety considerations, costs due to damage of equipment as a result of a failure of the device, and time lost during the shutdown of your operation dictate that the relays be inspected to verify their accuracy of service.
Testing will verify that the unit:
- is in good working order and has not suffered damage during shipping;
- has been correctly installed; and
- is set to protect the operation of your system.
In a typical industrial setup, testers must complete the following:
- Check the wiring diagram to validate the circuits and reference numbers of the interconnecting wiring.
- Inspect equipment for connections, wires on relay terminals, labels on equipment, etc.
- Test insulation resistance of all circuits.
- Run the relay self-test procedure, and check communications on digital/ numerical relays.
- Test main current transformers.
- Test main voltage transformers.
- Check that the settings on the relay alarm are correct.
- Check tripping and alarm circuits for accuracy.
Other checks that can also be run include:
- primary injection tests on each relay;
- secondary injection tests on each relay; and
- testing of protection scheme logic.
Many testing companies can provide you with detailed lists of their services for protection scheme testing.
Finding Reliable HV Relay Protection Testing Companies
If a shutdown is required to complete a thorough check of the relays and system, it is essential to select a company that has a successful record in performing the inspection within the scheduled time and without any incidents that might complicate the process. Consider the following points when selecting a testing agency:
- Length of Time in Operation: You will want to select a company with a clear track record of success. Check out the testimonials on their websites to gain an understanding of their values and methods of operation.
- Expertise: Often by visiting a company website you can view the qualifications of staff, their extent of communication, awards received, and government certifications. Check also to see what industry supply leaders they rely on to complete their core operations.
- Quotes: Reputable companies are willing to provide you with quotes about the cost of their services, availability and a proposed schedule of maintenance so that you can plan your strategy for the downtime.
- Similar Projects Completed: Check out any information about projects similar to yours that the company has completed.
- Responsiveness of Staff: If you do contact the company for information, it is a positive sign if you receive prompt, detailed information to all your questions. Expect that at times, competent staff may need to complete some research before outlining specific procedures that may interest you, whether it concerns recent government standards or specifics about the equipment onsite.
- Training: Many companies are willing to provide training or information for your staff to recognize problems before they become insurmountable and ways to remain safe while checking the HV relay protection system.
- Adaptability: Is the company willing to follow your well-established procedures that also help you to maintain functionality throughout the inspection?
Since your HV relay protection system is a vital component of your operations, regular testing is the first line of defense in making sure it is performing flawlessly to protect your working environment.